The invention relates to chillers (which may alternatively be referred to as coolers), particularly for bagged food products, of the type in which the bags are made to tumble in a bath of liquid coolant. Liquid or semi-liquid food products, such as soups and sauces, may be packaged after cooking in sealed plastic bags. In order to reduce the temperature of the food product, the bags may be introduced into a tumble chiller consisting of a drum which contains a coolant such as water or brine which is maintained at a temperature of approximately 0xc2x0 C. The drum rotates about a horizontal axis and serves to tumble the bags in the coolant and thereby promote cooling. After cooling, a door into the drum is opened. Some 20% of the bags fall out on their own, but the remainder must be removed manually.
An object of the invention is to provide a chiller which enables bags of food product to be introduced into a coolant, tumbled, and then removed after cooling, without manual handling.
In accordance with the invention, a chiller comprises a vessel for containing a liquid coolant, an endless conveyor, means for circulating the conveyor, and means for supporting the conveyor such that a run thereof descends into the vessel to form a loop within a coolant. The means for supporting the conveyor as so defined allow the length of the loop-forming run to be lengthened and shortened, as required. When the run is lengthened it forms a loop of sufficient volume to allow bags of food product to be tumbled in the coolant in which the conveyor run is immersed. In this mode of operation, the angle of the run at each of its ends is so steep that it cannot entrain and remove bags from the coolant. Flights on the conveyor may thereby serve as the means for causing the coolant to circulate and tumble the bags within the confines of the loop. When the loop-forming run is shortened, the loop becomes relatively shallow, and the run may serve to entrain and remove the bags from the coolant.
In a preferred embodiment of the invention, the loop-forming run passes over spaced-apart rollers, each of which is drivable in opposite directions, and at least one of which is drivable at two speeds at least, so as to allow a differential speed to be established between the two rollers. Rotation of the rollers so as to circulate the conveyor in one direction allows a second run of the conveyor (adjoining the loop-forming run) to be used to transport bags into the vessel during an initial phase of operation, where they accumulate in the space within the loop. Continued circulation of the conveyor may then be used to circulate the coolant and tumble the accumulated bags. Because of the steepness of the ends of the loop, the conveyor cannot entrain and remove the bags during this phase of operation. When the temperature of the bags has been reduced to a desired level, the rollers may be driven at different speeds so as to shorten the length of the run extending between them. When the desired reduction in the length of the run has been achieved, the rollers may again be driven at equal speeds. This reduction in the size of the loop and the gentle slope of the run at its ends during this latter phase allows the conveyor to entrain the bags and carry them out of the vessel. This latter phase of operation may be carried out with the conveyor circulating in the opposite direction to that during the first phase, in which case the bags are removed from the vessel on the same side as that at which they entered it. Alternatively, the latter phase may be carried out with the conveyor circulating in the same direction as during the initial phase, so that the bags are removed from the opposite side of the conveyor to that at which they entered it. Other arrangements may be used to lengthen and shorten the loop-forming run, and are contemplated by the invention. Thus, for example, one of the rollers supporting this run may be movable towards and away from the other roller.
It will be appreciated that any reduction in the length of the loop-forming run will be accompanied by an increase in the length of another run of the conveyor, so necessitating some means for taking up slack. Conveniently, an hydraulic or pneumatic ram mechanism is provided to support a further roller over which the conveyor passes. As the loop is shortened, the ram is extended to displace the further roller by the appropriate distance and prevent slack forming. Although it is preferred to use the conveyor to cause circulation of the coolant, other means may be used for this purpose and the conveyor used just to load and unload (or even just unload) the chiller.